A combination of radar and optics provides a system with inherently enhanced accuracy in the measurement of range, velocity and angular displacement, and improved countermeasure resistance. For example, laser radar is simply radar transformed from measuring reflected radio frequency electromagnetic radiation to locate spatially removed objects, to a system that operates on laser radiation. The high carrier frequency allows laser radar systems to be made more compact in physical dimension, which is particularly attractive in aircraft, projectile, space, and other volume-limited applications.
Disadvantageously, the penetrating ability of optical radiation is severely degraded by, for example, weather-related atmosphere disturbances. Consequently, the major developments in laser radar technology have been directed at range-finding capabilities, particularly as fire control for mobile and air defense weapon systems. Laser radar technology can also be used as a proximity fuzing device.
Laser radar systems typically use the time of travel of a reflected signal to calculate a range value. For example, briefly referring to FIG. 1, a laser radar system 100 transmits a pulse 102 to a target 106. The transmitted pulse 102 reflects from the target 106 in the form of a reflected pulse 104. The laser radar system 100 receives the reflected pulse 104 and determines the distance to the target based on the time of travel of the laser pulse. The resolution of the time of travel calculation, however, is limited to the length of the laser pulse utilized by the system. For at least this reason, short pulse lasers are ideally used to increase resolution. Additionally, measurement over long distances requires laser pulses to have high total energy levels for reliable reflected laser detection. The short pulses, however, are difficult to amplify to an energy level sufficient to achieve desirable long range performance. Longer pulses that are capable of containing sufficient energy, however, reduce the resolution to an undesirable level. Thus, a need exists in the industry to provide high-resolution long-range laser radar range detection.